Magnetic shoe attachment



J..F. NICHOLSON ETAL 3,031,778 MAGNETIC SHOE ATTACHMENT May 1, 1962 3 Sheets-Sheet 1 Filed Nov. 8. 1960 4 V/MM/% INVENTORS JAMES F. NICHOLSON DON W. NAA BY ATTQRNEYS y 1, 1962 J. F. NICHOLSON ETAL 3,031,778

MAGNETIC SHOE ATTACHMENT Filed Nov. 8, 1960 3 Sheets-Sheet 2 INVENTORS JAMES E NICHOLSON DON w. NA s BY 0% NQZAU in M ""4 ATTOR ZFEYS May 1, 1962 J. F. NICHOLSON ETAL 3,031,778

MAGNETIC SHOE ATTACHMENT Filed Nov. 8, 1960 3 Sheets-Sheet 3 INVENTO-RS" 0 JAMES E NICHOLSON 1 BY DON W.N'A

ATTOBNjS United Staes Patent The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to improved shoes and magnetic attachments for shoes that releasably attach to metal surfaces.

A background for acquiring an understanding of the present invention as it is claimed is provided by'the issued U.S. Patents Numbered 2,104,062 to I. C. Temple; 2,857,556 to R. W. Price, and the like.

A general statement of the exact nature, the substance, the operation, the purpose and the object of this invention as claimed is the provision of an improved shoe or shoe attachment that magnetically releasably attaches itself to and that releases itself from a magnetically attractive surface, such as plate steel, or the like, during standing and walking operations.

The object of this invention is to provide shoes, sandals, and the like, for standing and moving on a metal surface without failure and without undue fatigue during walking.

In the accompanying drawings:

FIG. 1 is a perspective view of a pair of shoe attachments or sandals that embody the present invention;

FIG. 2 is a view from above of the sandals in FIG. 1;

FIG. 3 is a view from below of the sandals in FIG. 1;

FIG. 4 is a circuit diagram of the electronics of the shoe attachment in FIG. 1;

FIG. 5 is a perspective view from below of a permanent magnet sandal; and

FIG. 6 is an axial section of the sensing device in FIG. 1.

In FIG. 1 of the accompanying drawings is a shoe attachment that comprises a sole 1 for being positioned beneath the foot or shoe to which the assembly is attached by suitable means, such as for example a toe or instep strap 2 and a heel strap 3.

The shoe attachment preferably comprises the sole 1, a pair of U-shaped horseshoe electromagnets 4 and 5 at the opposite ends of the sole 1, which electromagnets are energized by a pair of batteries 6 and 7 as power source of a magnitude established by the setting of a variable potentiometer 8. The potentiometer 8 is shunted out of circuit by an abrupt acceleration or deceleration by the operation of a sensing device 9 which automatically strengthens the magnetic field exerted by the electromagnets. The sole 1 is made of a non-ferromagnetic material such as sheet aluminum, or the like. The sole I may be strengthened intermediate its ends, if preferred, by a reinforcing plate 10 that illustratively may be of U-shaped section with its edges attached by rivets 11, or the like to the lower surface of the plate 1.

The toe and heel of the sole 1 having cushioning rubber 12 and 13 respectively cemented to the lower surfaces of the sole to minimize sliding and to cushion impact as steps are taken. A U-shaped, slotted clip 22 on a bolt 23 is available on the shoe sole contacted side of the sole 1 for engaging the forward edge of a shoe heel in making the engagement increasingly secure.

The toe horseshoe magnet 4 has opposed slots adjacent its spaced ends into which the opposite ends of a plate 14 below the sole 1 and the lateral edges of the plate 1 are ice positioned and are secured thereto by preferably welding or soldering or by the screws 15, or the like, as shown. The cores of the magnets 4 and 5 preferably are made of a non-rententive magnetic material, such as soft iron, transformer iron, silicon iron, and the like and preferably are cast as U-shaped units. In some installations one magnet instead of two or more is adequate, such for example, as where a magnet is positioned beneath the ball of the foot and no heel magnet is needed, or the reverse.

The heel horseshoe magnet 5 illustratively is inclined at an obtuse angle such as to the sole 1 for ease in slipping the device on a shoe. The heel magnet 5 has opposed slots adjacent its spaced ends with the lateral edges of the sole 1 and the ends of a plate 16 secured therein by welding, solder, or the like, or by screws 17, as shown. Each horseshoe magnet 4 and 5 comprises four separate coils of predetermined resistance and number of turns in place of single coils, as indicated in FIG. 4 of the drawings.

The power source batteries 6 and 7 preferably are connected in parallel through the windings of the magnets 4 and 5 since the parallel connection affords a longer service life out of the batteries than if they are connected in series because of the IR loss as heat in the potentiometer 8. The polarity of the batteries is reversible. The batteries 6 and 7 illustratively are 1 /2 volt batteries, such as are commonly used in flash lights, and the like.

The batteries 6 and 7 illustratively are held in place by spring clips, or the like, with a plate 18 of insulating material such as Plexiglas, Fiberglas, Bakelite, or the like, to which the spring clips are attached interposed between the spring clips and the magnet 4 by suitable means such as the screws 19, or the like. The electromagnets may if preferred be powered from an alternate power source such as may be built into a space suit, or from another source to minimize the mass to be lifted when steps are taken.

The circuitry in FIG. 4 indicates that the carbon poles of the batteries 6 and 7 are connected to the fixed terminal of the potentiometer 8 and the zinc poles of the batteries are connected to a normally oif, spring-loaded microswitch 20 that is secured by screws 21 to the bottom of the sole 1, as shown in FIG. 3. The microswitch interrupts current flow when the heel is raised illustratively inch. The location of the microswitch is determined by the rigidity of the sandal and by the characteristics of the microswitch. The microswitch facilitates walking inasmuch as the wearer is not required to break the total holding force of the magnets. It also allows the current to flow only when necessary to produce a magnetic force. This on-olf circuit greatly increases the operating life of the batteries.

Output from the microswitch 20 is to two cables in spaghetti tubing with four leads in each cable. The cables conduct to the parallel windings of the magnets 4 and 5 from which corresponding cables of four wires each connect with the movable contact of the potentiometer 8 as shown. The potentiometer is shunted by the sensing device 9, as indicated in FIGS. 4 and 6. The potentiometer allows the user to adjust the holding force of the shoes to his needs. The sensing device responds to abrupt motion of a predetermined value by shunting out the potentiometer.

The sensing device 9, shown in FIG. 6, comprises a hollow cylindrical tube 25 of Plexiglas, or the like, that has both of its ends closed by circular plates of the same insulating material cemented along the contacting edges. About midway of the axial length of and inside of the sensing device tube 25 a copper band 26 is mounted by bolts 27, or the like with one of the bolts connected, as

shown, with the variable tap of the potentiometer 8. The fixed terminal of the potentiometer 8 is connected to a bolt 28 in the upper end of the sensing device. The bolt 28 also supports a spring 29 at the lower end of which is attached a ball bearing 30 or similar mass, that is free to move radially of the sensing device and'touch the copper band 26 under acceleration or deceleration. The sensitivity of the sensing device 9 is determined by the space separating the ball 30 and the band 26, such for example as about inch or by the tension of the spring 29.

A permanent magnet shoe or shoe attachment is illustrated in FIG. of the accompanying drawings wherein a shoe sole 1' has riveted on its under side U-shaped cleats 35 and 36 for toe and heel straps 2' and 3' respectively. Beneath the ball of the shoe sole 1 in FIG. 5 are secured by pairs of bolts 37 a desired plurality of permanent magnets 38 with sponge rubber 31 between the sole and the magnets or not, as preferred. Beneath the heel of the shoe sole 1 in FIG. 5 are secured by pairs of bolts 39 a desired plurality of permanent magnets 40 with cushioning sponge rubber 32 between the sole and the magnets, if preferred. Bolts are preferred for these magnet mountings since magnets are discharged by being hammered, by aging and the like, and bolts provide replacement facilities. illustratively may be those marketed under the trade name Alnico S marketed by the Indiana Steel Products Company of Valparaiso, Indiana, or other magnets such as those of various AlNi-Fe compositions, and the like.

The apparatus that is described herein is substantially free from atmospheric pressure limitations but is subject to the temperature limitation that it must be used below the curie temperature limitations of its magnets. The aluminurn-nickel-iron composition magnets have no lower temperature limitations but their upper temperature limitation is about 500 C. The magnetic material preferably has a high inductance, such illustratively as the A'1-'-NiCo family.

In the use of'the electromagnetic form of'the device, the microswitch 20 serves to break the magnetic field and to release the magnetic power of attraction as the heel'is lifted from sheet steel without excessive exertion at the start of a stride and then reconnects the circuit at the heel impacting sheet steel as the foot next contacts its support.

It is to be understood that this disclosure applies to shoes that embody its teachings, sandals that fit on shoes and related installations without departing from its teachings. Changes and modifioationsin the materials contours, shapes and adaptationsoi the invention may be made Where comparable results are obtained thereby.

We claim:

1. A magnetic shoe comprising a sole, a magnet se- The magnets 38 and 40 cured to the sole, means releasably securing the magnet to the sole for the removal and the recharging of the magnet and its return to the sole in maintaining an optimum magnetic field strength in the magnet, a sensing device secured to the magnetic .shoe and responsive to abrupt motions to which the shoe is subjected, a microswitch secured to the magnetic shoe and controlling the flow of current through the magnet, and an adjustable potentiometer shunted by the sensing device and allowing the user of the shoe to adjust the holding force of the shoe to his needs.

2. A magnetic sandal for being attached to a shoe comprising a sole having upper and lower surfaces and a heel, cleat means'on said sandal sole, strap means ex tending through the cleat means and serving for attaching the sandal to the shoe, a first sole magnet'means secured to the sole and extending thereabove an adequate distance for the removable insertion of the toe of a shoe between the toe first magnet and the sandal sole, a heel second magnet means secured to the sandal heel. and extending thereabove for an adequate distance for the removable insertion of the heel of a shoe between the heel second -magnet and the sandal heel, and microswiteh means secured to the sandal and that automatically selectively deenergizes the toe first magnet and the heel second magnet between steps taken by the wearer of the sandal.

3. An electromagnetic shoe device comprising a sole with toe and heel portions, a U-shaped electromagnet bridging the sole toe portion and secured thereto, a U-shaped electromagnet bridging the sole heel portion and secured thereto, a power supply providing power to the electromagnets, and potentiometer means connected between the power supply and the electromagnets for adjusting the power flow therebetween.

4. The device defined by the above claim 3 inclusive of a microswitch for interrupting the power flow between the power supply and the electromagnets.

5. The device defined by the above claim 3 inclusive of a sensing device that shunts out the potentiometer when the device is subjected to abrupt motion of a predetermined value;

References Cited in the -fi],e of this patent UNITED STATES PATENTS 1,891,493 Apostolofr' Dec. 20, 1932 2,317,982 Diehl May 4, 1943 2,402,111 Engler June 11, 1946 2,595,694 Ogden May 6, v1952 2,683,194 Mathisen July 6, 1954 2,826,830 Nelson Mar. 18, 1958 2,932,910 Brown Apr. 19, 1960. 2,933,651 Legge Apr. 19, 1960 2,948,971 Shecter et a1. Aug. 16,1960 2,965,982 Saflir Dec. 27, 1960 

